Synergistic combination for treating herpes infections

ABSTRACT

Disclosed herein is a combination of an antiviral nucleoside analog and a ribonucleotide reductase inhibiting peptide derivative. The combination is useful for treating herpes infections.

FIELD OF THE INVENTION

This invention relates to an antiviral pharmaceutical compositioncomprising a combination of a nucleoside analog and a peptidederivative, and to a method of treating herpes infections in a mammal byadministering the combination to the mammal.

BACKGROUND OF THE INVENTION

Herpes viruses inflict a wide range of diseases against humans andanimals. For instance; herpes simplex viruses, types 1 and 2 (HSV-1 andHSV-2), are responsible for cold sores and genital lesions,respectively; varicella zoster virus (VZV) causes chicken pox andshingles; and the Epstein-Barr virus (EBV) causes infectiousmononucleosis.

Over the past two decades, a class of compounds known as the purine andpyrimidine nucleoside analogs has been the subject of much attention byinvestigators in the search for new therapeutic agents for the treatmentof herpes virus infections. As a result, several nucleoside analogs havebeen developed as antiviral agents. The most successful to date isacyclovir which is the agent of choice for treating genital herpessimplex infections. Other nucleoside analogs which are usedtherapeutically for the treatment of herpes infections includevidarabrine, idoxuridine, trifluridine and ganciclovir.

The mode of action by which the nucleoside analogs exert their antiviraleffect is thought to involve the inhibition of viral nucleic acidreplication. In the case of herpes viruses, the production of new viraldeoxyribonucleic acid (DNA), an essential stage of viral replication,depends on the interaction of the virally encoded enzyme, DNApolymerase, with cellular deoxynucleotides. The nucleoside analog, whenconverted enzymatically in vivo to its triphosphate derivative, acts asan alternate substrate (i.e. a "fraudulent substrate) for the viral DNApolymerase, and becomes incorporated into the growing viral DNA chain.Since the nucleoside analog either lacks and essential group, e.g. the3'-hydroxyl, or has the wrong stereochemistry, it also acts as a "chainterminator" of the growing viral DNA chain. The net effect is that thenucleoside analog acts in vivo as an inhibitor of the viral DNApolymerase.

Although the therapeutically useful nucleoside analogs have proven to bea valuable agents for combatting or controlling herpes infections, theagents are not without side effects. For example, skin rashes and renalimpairment have been reported as side effects for acyclovir (seePhysicians' Desk Reference, 44th ed., Medical Economics Inc., Oradell,N.J., USA, 1990, pp 819-821). For a recent review of the availableantiviral drugs and their side effects, see M. C. Nahata, "AntiviralDrugs: Pharmacokinetics, Adverse Effects, and Therapeutic Use", J.Pharm. Technol., 3, 100 (1987). Hence, safety as well as cost advantageswould be realized if these agents were formulated in a manner whichenhanced their therapeutic activity.

We now have found that the antiviral activity of the nucleoside analogscan be enhanced synergistically, without concomitant enhancement oftoxic effects, by combining the same with certain peptide derivativeshaving selective herpes ribonucleotide reductase inhibiting properties.

Ribonucleotide reductase (RR) is the enzyme responsible for theconversion of ribonucleotides to deoxyribonucleotides. The role of RR inDNA biosynthesis has been reviewed recently by J. Stubbe, J. Biol. Chem.265, 5329 (1990).

In 1985, T. Spector et al., Proc. Natl. Acad. Sci. USA, 82, 4254 (1985)reported that a combination of acyclovir and a semicarbazone RRinhibitor, 2-acetylpyridine thiosemicarbazone, produced a synergisticantiherpes effect. However, the combination of acyclovir with the RRinhibitor hydroxyurea was toxic to the host cell and acyclovir combinedwith some related semicarbazone derivatives did not always potentiatethe antiherpes activity of acyclovir.

A three-way combination of acyclovir, bacitracin and an RR inhibitingnonapeptide has been reported by E. A. Cohen et al., U.S. Pat. No.4,795,740, Jan. 3, 1989. Curiously, the antiherpes activity of thelatter combination was indicated as being equal or less than acycloviralone.

Still other synergistic combinations containing a nucleoside analog as acomponent have been reported; for example:

T. P. Zimmerman and G. Wolberg, European patent application 235931,published Sep. 9, 1987 (nucleoside analogs plus nucleoside transportinhibitors);

K. O. Smith, Canadian patent 1,239,093, issued Jul. 12, 1988 (nucleosideanalog plus an interferon);

T. Spector et al., Proc. Natl. Acad. Sci. USA, 86, 1051 (1989),(nucleoside analog plus RR inhibitor);

T. Spector et al., U.S. Pat. No. 4,758,572, issued Jul. 19, 1988(nucleoside analogs plus RR inhibitors); and

T. A. Blumenkopf et al, European patent application 349,243, publishedJan. 3, 1990 (nucleoside analogs plus RR inhibitors).

The combination of the present invention can be distinguished from thepreceding combinations by its different composition and/or its relativelack of toxicity.

SUMMARY OF THE INVENTION

Provided herein is a pharmaceutical composition for treating herpesinfections in a mammal comprising a pharmaceutically or veterinarilyacceptable carrier, and an effective amount of the combination of anantiviral nucleoside analog, or a therapeutically acceptable saltthereof, and a ribonucleotide reductase inhibiting peptide derivative offormula 1

    R.sup.1 NHC(O)CH.sub.2 CHR.sup.4 C(O)--NR.sup.3 --CH[CH.sub.2 C(O)--Y]C(O)--NH--CH[CR.sup.4 (R.sup.5)COOH]--C(O)--NH--CHR.sup.6 --Z 1

wherein R¹ is (1-10C)alkyl, (1-10C)alkyl monosubstituted with halo,hydroxy or lower alkoxy, lower cycloalkyl, (lower cycloalkyl)-(loweralkyl), phenyl(lower)alkyl or phenyl(lower)alkyl monosubstituted withhalo, hydroxy or lower alkoxy;

R² is lower alkyl;

R³ is hydrogen or lower alkyl;

R⁴ is hydrogen or lower alkyl and R⁵ is lower alkyl, or R⁴ and R⁵together with the carbon atom to which they are attached form a lowercycloalkyl;

R⁶ is lower alkyl, lower cycloalkyl or (lower cycloalkyl)-(lower alkyl);

Y is

(a) NR⁷ R⁸ wherein R⁷ and R⁸ each independently is lower alkyl, or R⁷and R⁸ together with the nitrogen atom to which they are attached form apyrrolidino, piperidino, morpholino, thiomorpholimo, piperazino or N⁴-methylpiperazino; or

(b) (1-7C)alkyl, lower cycloalkyl or (lower cycloalkyl)methyl; and

Z is hydrogen, COOH or CH₂ OH;

or a therapeutically acceptable salt thereof.

The antiviral nucleoside analog employed in the combination is one whichis enzymatically convertible (in vivo) to a viral DNA polymeraseinhibitor of, and/or an alternative substrate for, a herpes DNApolymerase. The antiviral nucleoside analog can be selected from knownnucleoside analogs. Preferred nucleoside analogs of the inventioninclude acyclovir and its analogs; for example, the compounds of formula2 ##STR1## wherein R⁹ is hydrogen, hydroxy or amino, or atherapeutically acceptable salt thereof. (Formula 2 wherein R⁹ ishydroxy represents acyclovir.)

Other preferred antiviral nucleoside analogs for use according to thepresent invention include vidarabine, idoxuridine, trifluridine,ganciclovir, edoxudine, brovavir, fiacitabine, penciclovir, famciclovirand rociclovir.

A preferred group of the peptide derivatives for use according to thepresent invention is represented by formula 1 wherein R¹ is(1-10C)alkyl, (1-10C)alkyl monosubstituted with halo, hydroxy or loweralkoxy, lower cycloalkyl or (lower cycloalkyl)methyl, R² is lower alkyl,R³ is hydrogen, R⁴ and R⁵ together with the hydrogen to which they areattached form a lower cycloalkyl, and R⁶, Y and Z are as definedhereinabove; or a therapeutically acceptable salt thereof.

A more preferred group of the peptides derivatives is represented byformula 1 wherein R¹ is 1-methylethyl, 1-methylpropyl, 1-ethylpropyl,1-methylbutyl, cyclopentyl or cyclohexyl, R² is methyl, ethyl, propyl,1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethylor 1-methylbutyl, R³, R⁴ and R⁵ are as defined hereinabove, R⁶ is1-methylethyl, 1,1-dimethylethyl, 1-methylpropyl, 2-methylpropyl,2,2-dimethylpropyl, cyclopentyl, cyclohexyl or cyclohexylmethyl, Y isNR⁷ R⁸ wherein R⁷ and R⁸ each independently is methyl, ethyl or propylor R⁷ and R⁸ together with the nitrogen atom to which they are attachedform a pyrrolidino, piperidino, morpholino or N⁴ -methylpiperazino, or Yis pentyl, hexyl, 4-methylpentyl, heptyl, cyclopentyl or cyclohexyl, andZ is as defined hereinabove; or a therapeutically acceptable saltthereof.

A most preferred group of the peptide derivatives is represented byformula 1 wherein R¹ is 1-methylethyl or 1-ethylpropyl, R² is1-methylethyl or 1,1-dimethylethyl, R³ is hydrogen, R⁴ and R⁵ togetherwith the carbon atom to which they are attached form a cyclobutyl orcyclopentyl, R⁶ is 2,2-dimethylpropyl, Y is N,N-dimethylamino,N,N-diethylamino, pyrrolidino, morpholino or N⁴ -methylpiperazino,hexyl, heptyl or cyclopentyl, and Z is as defined hereinabove; or atherapeutically acceptable salt thereof.

Included within the scope of the invention is a cosmetic compositioncomprising a herpes viral prophylactic amount of the combination of anantiviral nucleoside analog of formula 2 wherein R⁹ is a defined hereinabove, or a therapeutically acceptable salt thereof; a ribonucleotidereductase inhibiting peptide derivative of formula 1, or atherapeutically acceptable salt thereof; and a physiologicallyacceptable carrier.

Also included is a method of treating herpes viral infections in amammal which comprises administering thereto an effective amount of acombination of an antiviral nucleoside analog and the ribonucleotidereductase inhibiting peptide derivative of formula 1, or atherapeutically acceptable salt thereof.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an isobologram showing the synergistic inhibition of HSV-2replication by the peptide of formula 1, Et₂ CHNH--COCH₂ CH[(S)-C(CH₃)₃]CO-Asp(pyrrolidino)-Asp(cyPn)-ΥMeLeu-OH and acyclovir (see example 6).The concentration of the peptide was varied and the inhibition of virusreplication was assessed. The FIC60 (acyclovir) is the ratio of theconcentration of acyclovir required tip inhibit virus replication by 60%in the presence of a given concentration of the peptide. The x axis isthe ratio of a given concentration of the peptide to the concentrationthe peptide producing 60% inhibition of virus replication in the absenceof acyclovir.

DETAILS OF THE INVENTION

The antiviral nucleoside analogs, and their therapeutically acceptablesalts, for use according to the present invention are a well known classof compounds. As noted above, the members of this class arecharacterized by the manner in which they mediate an antiviral effectagainst herpes viruses, i.e. by in vivo inhibition of viral DNApolymerase. Important members of this class are acyclovir and itsanalogs which are described by H. J. Schaeffer in U.S. Pat. No.4,199,574, issued Apr. 22, 1980; see also H. J. Schaeffer et al., Nature(London), 272, 583 (1978) and T. A. Krenitsk et al., Proc. Natl. Acad.Sci. USA, 81, 3209 (1984). The compound of formula 2 wherein R⁹ ishydroxy is "acyclovir", also known by its chemical name,9-[(2-hydroxyethoxy)methyl]guanine. The compound of formula 2 wherein R⁹is hydrogen has the names 6-deoxyacyclovir and2-amino-9-[(2-hydroxyethoxy)methyl]adenine; and the compound of formula2 wherein R⁹ is amino has the chemical name,2,6-diamino-9-[(2-hydroxyethoxy)methyl]purine.

Is to be understood that the compound of formula 2 in which R⁹ ishydroxy can exist in its tautomeric form, i.e.2-amino-1,9-dihydro-9-[(2-hydroxyethoxy)methyl)-6H-purin-6-one, and thatthe compound can be a mixture of the two tautomeric forms, thepercentage of each tautomer in the mixture being dependent on thephysical environment of the compound. Tautomeric forms also are possiblefor the other antiviral nucleoside analogs having an enolizablecarbonyl.

Other antiviral nucleotides contemplated for use according to thepresent invention include vidarabine (9-β-D-arabinofuranosyladeninemonohydrate), see R. J. Whitley et al., N. Engl. J. Med., 307, 971(1982); idoxudine (2'-deoxy-5-iodouridine), see W. H. Prusoff, Biochim.Biophys. Acta, 32, 295 (1959); trifluridine[2'-deoxy-5-(trifluoro-methyl)-uridine], see C. Heidelberger, U.S. Pat.No. 3,201,387, issued Aug. 17, 1965; ganciclovir9-[(1,3-dihydroxy-2-propoxy)methyl]guanine, see J. P. Verheyden and J.C. Martin, U.S. Pat. No. 4,355,032, issued Oct. 19, 1982; edoxudine(5-ethyl-2'-deoxyuridine), see K. K. Gauri, U.S. Pat. No. 3,553,192,issued Jan. 5, 1971; brovavir [(E)-5-(2-bromovinyl)-2'-deoxyuridine],see Y. Benoit et al., Eur. J. Pediatrics, 143, 198 (1985); fiacitabine(2'-fluoro-deoxy-5-iodouridine), see B. Leyland-Jones et al., J. Infect.Dis., 154, 430 (1986), penciclovir(9-[4-hydroxy-3-(hydroxymethyl)butyl]guanine, see S. E. Fowler et al.,Br. J. Clin. Pharmacol., 28, 236P (1989); famciclovir(9-[4-acetoxy-3-(acetoxy-methyl)butyl]adenine, see R. A. V. Hodge etal., Antimicrob. Agents Chemotherap., 33, 1765 (1989); and rociclovir(9-[(1,3-diisopropoxy-2-propoxy)methyl]adenine, see E. Winklemann etal., Arzneim.-Forsch., 38, 1545 (1988).

For convenience, the RR inhibiting peptide derivatives of this inventionare sometimes designated hereinafter as the peptides of formula 1.

With reference to the peptides of formula 1, the abbreviations usedherein for designating the amino acids and the protective groups arebased on recommendations of the IUPAC-IUB Commission of BiochemicalNomenclature, see European Journal of Biochemistry, 138, 9 (1984). Forinstance, Val, Ala, Ile, Asp and Leu, represent the residues ofL-valine, L-alanine, L-isoleucine, L-aspartic acid and L-leucine,respectively.

The asymmetric carbon atoms residing in the principal linear axis (i.e.the backbone) of the peptides of formula 1, exclusive of the1,4-dioxobutyl moiety and the terminal groups, have an S configuration.Asymmetric carbon atoms residing in the side chain of an amino acid orderived amino acid residue, in the 1,4-dioxobutyl moiety or in aterminal group, may have the S or R configuration.

The term "residue" with reference to an amino acid or amino acidderivative means a radical derived from the corresponding α-amino acidby eliminating the hydroxyl of the carboxy group and one hydrogen of theα-amino group.

The term "halo" as used herein means a halo radical selected from bromo,chloro, fluoro or iodo.

The term "lower alkyl" as used herein, either alone or in combinationwith a radical, means straight chain alkyl radicals containing one tosix carbon atoms and branched chain alkyl radicals containing three tosix carbon atoms and includes methyl, ethyl, propyl, butyl, hexyl,1-methylethyl, 1-methylpropyl, 2-methylpropyl and 1,1-dimethylethyl. Theterm "(1-7C)alkyl" as used herein means straight chain alkyl radicalscontaining one to seven carbon atoms and branched chain alkyl radicalscontaining three to seven carbon atoms. The term "(1-10C)alkyl"similarly contemplates those alkyl radicals containing from one to tencarbon atoms.

The term "lower cycloalkyl" as used herein, either alone or incombination with a radical, means saturated cyclic hydrocarbon radicalscontaining from three to six carbon atoms and includes cyclopropyl,cyclobutyl, cyclopentyl and cyclohexyl.

The term "lower alkoxy" as used herein means straight chain alkoxyradicals containing one to four carbon atoms and branched chain alkoxyradicals containing three to four carbon atoms and includes methoxy,ethoxy, propoxy, 1-methylethoxy, butoxy and 1,1-dimethylethoxy. Thelatter radical is known commonly as tertiary-butyloxy.

The symbol "Tbg" represents the amino acid residue of2(S)-amino-3,3-dimethylbutanoic acid. The symbol "Cpg" represents theamino acid residue of (S)-α-aminocyclopentaneacetic acid. The symbol"Cha" represents the amino acid residue of(S)-α-aminocyclohexanepropionic acid. The term "ΥMe-Leu" represents theamino acid residue of 2(S)-amino-4,4-dimethylpentanoic acid.

Other symbols used herein are: (N-Me)Asp for the residue of(S)-2-(methylamino)butanedioic acid; Asp(cyBu) for the residue of(S)-α-amino-1-carboxycyclobutaneacetic acid; Asp(cyPn) for the residue(S)-α-amino-1-carboxycyclopentaneacetic acid; Asp(pyrrolidino) for theresidue of the amide 2(S)-α-amino-4-oxo-4-pyrrolidinobutanoic acid; andAsp(morpholino) and Asp(NEt₂) similarly represent the residues of thecorresponding amides wherein the pyrrolidino is replaced with morpholinoand diethylamino respectively. The symbol "Asp(diMe) represents theresidue of 2(S)-amino-3,3-dimethylbutanedioic acid, i.e.3,3-dimethyl-L-aspartic acid.

The ribonucleotide reductase (RR) inhibiting peptides of formula 1, andtheir therapeutically acceptable salts, are prepared by processesdescribed by P. L. Beaulieu, R. Deziel and N. Moss in U.S. patentapplication Ser. No. 711,232, filed Jun. 6, 1991. More specifically, thepeptides of formula 1 can be prepared by processes which incorporatetherein methods commonly used in peptide synthesis such as classicalsolution coupling of amino acid residues and/or peptide fragments, andif desired solid phase techniques. Such methods are described, forexample, by E. Schroder and K. Lubke, "The Peptides", Vol. 1, AcademicPress, New York, N.Y., 1965, pp 2-128, in the textbook series, "ThePeptides: Analysis, Synthesis, Biology", E. Gross et al., Eds., AcademicPress, New York, N.Y., 1979-1987, Volumes 1 to 8, and by J. M. Stewartand J. D. Young in "Solid Phase Peptide Synthesis", 2nd ed., PierceChem. Co., Rockford, Ill., USA, 1984.

A common feature of the aforementioned processes for the peptides is theprotection of the reactive side chain groups of the various amino acidresidues or derived amino acid residues with suitable protective groupswhich will prevent a chemical reaction from occurring at that site untilthe protective group is ultimately removed. Usually also common is theprotection of an α-amino group on an amino acid or a fragment while thatentity reacts at the carboxy group, followed by the selective removal ofthe α-amino protective group to allow subsequent reaction to take placeat that location. Usually another common feature is the initialprotection of the C-terminal carboxyl of the amino acid residue orpeptide fragment, if present, which is to become the C-terminal functionof the peptide, with a suitable protective group which will prevent achemical reaction from occurring at that site until the protective groupis removed after the desired sequence of the peptide has been assembled.

In general, therefore, a peptide of formula 1 can be prepared by thestepwise coupling in the order of the sequence of the peptide of theamino acid or derived amino acid residues, or fragments of the peptide,which if required are suitably protected, and eliminating all protectinggroups, if present, at the completion of the stepwise coupling to obtainthe peptide of formula 1.

The term "pharmaceutically acceptable carrier" as used herein means anon-toxic, generally inert vehicle for the active ingredients, whichdoes not adversely affect the active ingredients.

The term "physiologically acceptable carrier" as used herein means anacceptable cosmetic vehicle of one or more non-toxic excipients which donot react with or reduce the effectiveness of the active ingredientscontained therein.

The term "veterinarily acceptable carrier" as used herein means aphysiologically acceptable vehicle for administering drug substances todomestic animals comprising one or more non-toxic pharmaceuticallyacceptable excipients which do not react with the drug substance orreduce its effectiveness.

The term "effective amount" means a predetermined antiviral amount ofthe antiviral agent, i.e. an amount of the agent sufficient to beeffective against the viral organisms in vivo.

The term "synergistic effect" when used in relation to the antiviral orantiherpes activity of the above defined combination of the nucleosideanalog and peptide of formula 1 means an antiviral or antiherpes effectwhich is greater than the predictive additive effect of the twoindividual components of the combination.

The antiviral activity of the combination of this invention can bedemonstrated by biochemical, microbiological and biological proceduresshowing the inhibitory effect of the combination on the replication ofHSV-1 and HSV-2, and other herpes viruses, for example, varicella zostervirus (VZV), Epstein-Barr virus (EBV), equine herpes virus (EHV) andpseudorabies virus (PRV).

For example, a method for demonstrating the inhibitory effect of thecombination on viral replication is the cell culture technique; see, forexample, T. Spector et al., Proc. Natl. Acad. Sci. USA, 82, 4254 (1985).This method in a modified form is exemplified hereinafter.

A method for demonstrating the therapeutic effect of the combination isthe guinea pig model for cutaneous herpes simplex viral infections; see,for example, S. Alenius and B. Oberg, Archives of Virology, 58, 277(1978).

When utilizing the combination of this invention for treating viralinfections, the combination is administered to warm blooded animals,e.g. humans, pigs or horses, in a vehicle comprising one or morepharmaceutically acceptable carriers, the proportion of which isdetermined by the solubility and chemical nature of the nucleosideanalog and the peptide of formula 1, chosen route of administration,standard biological practice, and by the relative amounts of the twoactive ingredients to provide a synergistic antiviral effect.Preferably, the combination is administered topically. For example, thetwo active agents (i.e. the antiviral nucleoside analog and the peptideof formula 1, or their therapeutically acceptable salts) can beformulated in the form of solutions, emulsions, creams, or lotions inpharmaceutically acceptable vehicles. Such formulation can contain0.01-1.0%, preferably 0.05-0.5%, by weight of the nucleoside analog, ora therapeutically acceptable salt thereof, and about 0.5-20%, preferably1-10%, by weight of the peptide of formula 1, or a therapeuticallyacceptable salt thereof.

In any event, the two active agents are present in the pharmaceuticalcomposition in amounts to provide a synergistic antiherpes effect.

One preferred embodiment of this invention involves an antiviralpharmaceutical composition for treating herpes viral infections of theskin or part of the oral or genital cavity. This composition comprises acombination of 0.05-1.0% by weight of the nucleoside analog of formula 2in which R⁹ is hydroxy, 1-10% by weight of the peptide of formula 1wherein R² is 1,1-dimethylethyl (with an orientation that imparts an (S)configuration to the 1,4-dioxo moiety), R⁴ and R⁵ together with thecarbon atom to which they are attached form a cyclobutyl or cyclopentyland R⁶ is 2,2-dimethylpropyl, together with a pharmaceuticallyacceptable carrier. Preferred carriers in this instance are watersoluble ointment bases or water-oil type emulsions.

Examples of suitable excipients or carriers for the above mentionedformulations are found in standard pharmaceutical texts, e.g. in"Remington's Pharmaceutical Sciences", 18th ed, Mack Publishing Company,Easton, Pa., 1990.

The dosage of the combination of this invention will vary with the formof administration and the particular active agents chosen for thecombination. Furthermore, it will vary with the particular host undertreatment. Generally, treatment is initiated with small dosagessubstantially less than the optimum dose of the combination. Thereafter,the dosage is increased by small increments until the optimum effectunder the circumstances is reached. In general, the combination is mostdesirably administered at a concentration level that will generallyafford antiviral effective results against herpes virus without causingany harmful or deleterious side effects.

The combinations is administered topically to the infected area of thebody, e.g. the skin or part of the oral or genital cavity, in an amountsufficient to cover the infected area. The treatment should be repeated,for example, every four to six hours until lesions heal.

Although the method of treating herpes viral infections can be mostadvantageously practised by administering the combination of thenucleoside analog and the peptide of formula 1 simultaneously in aformulation, the separate or sequential administration on a daily basisof the two active agents is also encompassed within the scope of thisinvention.

Another embodiment of this invention comprises a cosmetic compositioncomprising a herpes viral prophylactic amount of the combination of thisinvention, together with a physiologically acceptable cosmetic carrier.Additional components, for example, skin softeners, may be included inthe formulations. The cosmetic formulation of this invention is usedprophylactically to prevent the outbreak of herpetic lesions. They canbe applied nightly and generally contain less of the two active agentsof the combination than pharmaceutical preparations. A preferred rangefor the amount of each of the agents in the cosmetic composition is0.01-0.1% by weight of the nucleoside analog and 0.1 to 1% by weight ofthe peptide of formula 1.

The following examples illustrate further this invention. Solutionpercentages or ratios express volume to volume relationship, unlessstated otherwise. Abbreviations used in the examples include; Boc:t-butyloxy-carbonyl; BOP:(benzotriazol-1-yloxy)tris(dimethylamino)-phosphoniumhexafluorophosphate; Bzl: benzyl; CH₂ Cl₂ : methylenedichloride; DIPEA:diisopropylethylamine; DCC: N,N-dicyclohexylcarbodiimide; DMF: dimethylformamide; Et₂ O: diethyl ether; EtOAc: ethyl acetate; EtOH: ethanol;HOBt: 1-hydroxybenzotriazole; HPLC: high performance liquidchromatography; MeOH: methanol; NMM: N-methylmorpholine; TFA:trifluoroacetic acid; THF: tetrahydrofuran; TLC: thin layerchromatography. Temperatures are given in degrees centrigrade.

EXAMPLE 1 Preparation of the Intermediate Boc-Asp(pyrrolidino)-OH

N,N'-Carbonyldiimidazole (24.32 g, 0.15 mol) was added in small portionsto a stirred solution of Boc-Asp-OBzl (47.60 g, 0,147 mol) inacetonitrile (500 mL). After 45 min, the reaction mixture was cooled to0° and pyrrolidine (13.4 mL, 0.16 mol) was added dropwise. Thereafter,the mixture was stirred at room temperature to complete the reaction(about 3 h as judged by TLC). The solvent was removed under reducedpressure and the residue was dissolved in EtOAc (500 mL). The organicphase was washed with 10% aqueous HCl (3×100 mL), 1N aqueous NaOH (2×100mL) and dried (MgSO₄). Evaporation of the organic phase under reducedpressure gave a colorless oil which solidified on standing. The latterproduct in a solution of EtOH (200 mL) was subjected to hydrogenolysisfor 20 h at atmospheric pressure using 200 mg of 20% by weight ofPd(OH)₂ on carbon as the catalyst. The reaction mixture was filteredthrough diatomaceous earth. Evaporation of the filtrate afforded aresidue which was purified by recrystallization from hexane/Et₂ O togive the desired product (37.10 g, 88%), mp 114°-116°. The structure ofthe product was confirmed by NMR.

Corresponding N-substituted asparagine analogs were obtained byreplacing pyrrolidine in the procedure of this example with theappropriate amine (e.g. diethylamine or piperidine).

(b) Preparation of the Intermediate Boc-2(S)-Amino-4-oxo-undecanoic Acid

Boc-Asp-OBzl (500 mg, 1.55 mmol) was dissolved in acetonitrile (10 mL)and N,N'-carbonyldiimidazole (277 mg, 1.71 mmol) was added to thesolution. After 30 min, p-nitrobenzyl-magnesium malonate (860 mg, 1.71mmol) was added and the mixture was stirred at room temperature(20°-22°) for 1.5 h. The acetonitrile was evaporated. The residue wasdissolved in EtOAc, washed with 1N aqueous HCl, water and then brine.The organic phase was dried (MgSO₄) and concentrated under reducedpressure. The resulting residue was purified by chromatography (SiO₂,eluent: hexane-EtOAc) to give Boc-2(S)-amino-4-oxo-1,6-hexanedioic acid1-benzyl ester 6-(4-nitrophenyl)methyl ester (600 mg, 80%). The lattercompound (3.25 g, 6.5 mmol) was dissolved in DMF (40 mL). Cs₂ CO₃ (2.33g, 7.14 mmol) and hexyl iodide (1.51 g, 7.14 mmol) were added to thesolution. The mixture was stirred at room temperature for 18 h. Thesolvent was evaporated. The residue was dissolved in EtOAc. The solutionwas washed with 1N aqueous HCl and H₂ O, dried (MgSO₄) and evaporated.The residue was purified by chromatography (SiO₂, eluent=hexane-EtOAc)to giveBoc-2(S)-amino-4-oxo-5-[(4-nitrophenyl)methoxycarbonyl]undecanoic acidbenzyl ester (630 mg). A solution of the latter compound (630 mg) inMeOH (25 mL) was shaken on a Parr apparatus under an atmosphere of H₂ inthe presence of 20% Pd(OH)₂ /C (70 mg) for 18 h. After filtration andconcentration of the reaction mixture, the resulting residue wasdissolved in EtOAc. The solution was stirred with 1N aqueous HCl for 10min. The organic phase was separated, washed with H₂ O, dried (MgSO₄)and evaporated. The residue was purified by chromatography (SiO₂,eluent: hexane-EtOAc) to give the title compound (160 mg). NMR and MS ofthe product were in agreement with the expected structure.

The coupling of the latter intermediate with appropriate units for thepreparation of peptides of formula 1 in which Y is heptyl was achievedwith DCC/HOBt as the coupling agent.

(c) Preparation of the IntermediateBoc-2(S)-Amino-5-cyclopentyl-4-oxocyclopentanoic Acid

Boc-2(S)-amino-4-oxo-1,6-hexanedioic acid 1-benzyl ester6-(4-nitrophenyl)methyl ester (4.8 g, 9.6 mmol) was dissolved in DMF(100 mL). Na₂ CO₃ (4.07 g, 38.4 mmol) and 1,4-diiodobutane (3.59 g, 11.6mmol) were added to the solution. The mixture was stirred 18 h at roomtemperature and then heated at 50° for 3 h. Evaporation of the reactionmixture, extraction of the resulting residue with EtOAc, washing of theextract with 1N aqueous HCl and water, drying (MgSO₄) and evaporation ofthe extract gave a crude product. The crude product was purified bychromatography (SiO₂, eluent: hexane-EtOAc) to give the correspondingbenzyl ester of the title compound (4.3 g). The benzyl ester of thelatter compound was subjected to hydrogenolysis [5% Pd(OH₂)/C in MeOH,18 h] and worked up (see section (a) of this example) to give the titlecompound (140 mg). NMR and MS of the product were in agreement with theexpected structure.

The coupling of the latter intermediate with other appropriate units forthe preparation of peptides of formula 1 in which Y is cyclopentyl wasachieved with BOP.

EXAMPLE 2 Preparation of(S)-α-Azido-1-[(phenylmethoxy)carbonyl]cyclopentaneacetic Acid BenzylEster

The title compound was prepared from 2-oxaspiro[4.4]nonane-1,3-dione,described by M. N. Aboul-Enein et al., Pharm. Acta Helv., 55, 50 (1980),according to the asymmetric azidation method utilizing the Evan'sauxiliary, see D. A. Evans et al., J. Amer. Chem. Soc., 112, 4011(1990). The NMR (200 MHz, CDCl₃) of the compound showed: δ 4.55 (s,1H),5.12 (s,2H) and 7.4 (m,5H).

EXAMPLE 3 Preparation of(R,S)-3-(1,1-dimethylethyl)-dihydro-2,5-furandione

(a) A mixture of pivaldehyde (5.00 g, 58 mmol), ethylcyanoacetate (6.60g, 58.3 mmol), acetic acid (3.50 g, 58.3 mmol) and pyridine (4.60 g,58.2 mmol) was heated at reflux for 1 h. A second portion of pivaldehyde(5.00 g, 58 mmol) was added. The refluxing of the mixture was continuedfor 18 h. After cooling, the mixture was poured into 1N aqueous HCl (50mL). The resulting mixture was extracted with EtOAc (3×50 mL). Thecombined organic layers were washed with 1N aqueous HCl, dried (MgSO₄)and concentrated to give a colorless oil. The oil was purified by flashchromatography on SiO₂ using hexane-EtOAc (9:1) as the eluant to give2-cyano-4,4-dimethyl-2-pentenoic acid ethyl ester as a colorless oil(7.69 g, 73% yield).

(b) The latter compound (7.69 g, 42.4 mmol) was mixed with glacial AcOH(2.60 g, 43 mmol) and anhydrous pyridine (3.42 g, 43 mmol). The mixturewas heated to 50°. Potassium cyanide was added, followed by the additionof anhydrous EtOH (6 mL). The mixture was heated at 50° for 45 min,cooled to room temperature and partitioned between 1N aqueous HCl (25mL) and Et₂ O (100 mL). The Et₂ O layer was separated, washed with 1Naqueous HCl (2×20 mL) and brine (2×20 mL), dried (MgSO₄) andconcentrated to give 2,3-dicyano-4,4-dimethylpentanoic acid ethyl esteras a brown oil (8.83 g, 100% crude yield).

(c) The latter product (11 g) was suspended in concentrated HCl (150mL). The mixture was heated at reflux for 24 h and then cooled in an icebath. The resulting white solid precipitate was collected, washed withwater and dried under vacuum. The solid was dissolved in EtOAc (300 mL).Insoluble material in the solution was removed by filtration. Thefiltrate was concentrated under reduced pressure to give an oil. The oilwas triturated with hexane. The resulting white crystalline material wascollected to give (R,S)-2-(1,1-dimethylethyl)-1,4-butanedioic acid (7.95g, 95% yield).

(d) The latter compound (7.95 g, 51 mmol) was suspended in aceticanhydride (11 mL, 117 mmol). The mixture was heated at 110° for 2 h.Subsequent distillation under vacuum of the mixture gave the titlecompound of this example as an oil (bp 140°-145°/12 mm, 7.08 g, 88%yield). The oil solidified upon cooling.

EXAMPLE 4 Preparation of(R,S)-2-(1,1-Dimethylethyl)-4-oxo-4-(1-ethylpropylamino)butanoic Acid

(R,S)-3-(1,1-dimethylethyl)-dihydro-2,5-furandione (5.00 g, 32 mmol,described in example 3) was dissolved in acetonitrile (50 mL). Thesolution was cooled to 0°. (1-Ethylpropyl)amine (6.13 g), 70.4 mmol) wasadded slowly to the stirred solution. The solution was stirred at roomtemperature for 18 h and then partioned between Et₂ O and 10% aqueouscitric acid (60 mL each). The organic phase was separated. The aqueousphase was extracted with Et₂ O (3×25 mL). The combined organic layerswere washed with 10% aqueous citric acid (2×25 mL), brine (25 mL), dried(MgSO₄) and concentrated. The residue was triturated with Et₂ O to givethe title compound as a white solid (4.65 g, 59% yield).

EXAMPLE 5 Preparation of Et₂ CHNH-COCH₂ CH[(S)-C(CH₃)₃]CO-Asp(pyrrolidino)-Asp(cyPn)-ΥMeLeu-OH

(a) A solution of Boc-ΥMeLeu-OBzl (0.272 g, 0.81 mmol) in 30% TFA in CH₂Cl₂ was stirred at 0° for 1 h. The solvent was evaporated and theresidue was dried under vacuum. The resulting TFA salt was dissolved inacetonitrile (20 mL). NMM (0.53 mL, 4.86 mmol) was added to thesolution, followed by the addition of(S)-α-azido-1-[(phenylmethoxy)carbonyl]cyclopentaneacetic acid (0.269 g,0.89 mmol, described in example 2) and BOP (0.464 g, 1.05 mmol). Themixture was stirred at room temperature for 18 h. The solvent wasevaporated. The residue was dissolved in EtOAc (50 mL). The solution waswashed with 10% aqueous HCl (2×25 mL), a saturated aqueous solution ofNa₂ CO₃ (2×25 mL) and brine (25 mL). Evaporation of the organic phasegaveN-{(S)-α-azido-1-[(phenylmethoxy)carbonyl]cyclopentaneacetyl}-2(S)-amino-4,4-dimethylpentanoicacid benzyl ester as a yellow oil (0.400 g, 96% yield).

(b) A solution of the latter compound (0.312 g, 0.6 mmol) in MeOH (20mL) was added dropwise to a solution of SnCl₂ (0.207 g, 1.2 mmol) inMeOH (10 mL) at 0°. The mixture was stirred under argon for 4 h whilethe reaction temperature was allowed to come to room temperature. Thereaction mixture was concentrated under reduced pressure. The residuewas dissolved in EtOAc (50 mL). The solution was rendered basic by theaddition of 5% aqueous NaHCO₃. The organic phase was separated, washedwith H₂ O (20 mL) and brine (20 mL), dried over anhydrous K₂ CO₃,filtered and concentrated to dryness to giveN-{(S)-α-amino-1-[(phenylmethoxy)carbonyl]cyclopentaneacetyl}-2(S)-amino-4,4-dimethylpentanoicacid benzyl ester as a white solid (0.300 g, 0.6 mmol).

(c) The latter amine was dissolved in acetonitrile (20 mL). NMM (0.39mL, 3.6 mmol), Boc-Asp(pyrrolidino)-OH (0.343 g, 1.2 mmol, described inexample 1) and BOP (0.583 g, 1.32 mmol) were added to the solution. Themixture was stirred at room temperature for 18 h. The solvent wasevaporated and the residue was dissolved in EtOAc (50 mL). The solutionwas washed with 10% aqueous HCl (2×20 mL), a saturated aqueous solutionof Na₂ CO₃ and brine. Thereafter, the solution was dried (MgSO₄) andconcentrated to dryness. The residue was purified by flashchromatography [SiO₂, eluant=EtOAc-hexane, 1:1)] to giveN'-[N-(tertiary-butyloxycarbonyl)-2(S)-amino-4-oxo-4-pyrrolidinobutanoyl]-N-{α-amino-1-[(phenylmethoxy)carbonyl]cyclopentane-acetyl}-2(S)-amino-4,4-dimethylpentanoicacid benzyl ester [Boc-Asp(pyrrolidino)-Asp(cyPn)-ΥMeLeu-OH dibenzoate]as a colorless foam (0.459 g, 100%).

(d) A solution of the latter compound (0.385 g, 0.5 mmol) in 30% TFA inCH₂ Cl₂ was stirred at 0° for 1 h. The solvent was evaporated and theresidue was dried under vacuum. The resulting TFA salt, dissolved inacetonitrile (20 mL), was coupled with(R,S)-2-(1,1-dimethylethyl)-4-oxo-4-(1-ethyl-propylamino)butanoic acid(0.146 g, 0.6 mmol, described in example 4) using BOP (0.309 g, 0.7mmol) and NMM (0.65 mL, 6 mmol) according to the procedure described inparagraph (c) of this example. The resulting product was a mixture oftwo diastereoisomers. The isomers were separated by flash chromatography(SiO₂, eluant=EtOAc) to give a less polar isomer (0.100 g, Rf 0.71(EtOAc)] and a more polar isomer [0.120 g, Rf 0.42 (EtOAc)]. The morepolar isomer, namely the di(benzyl ester) of the title compound of thisexample, was subjected to hydrogenolysis (10% Pd/C in EtOH, 1 atmosphereof H₂, 3 h]. After the completion of the reaction, the catalyst wasremoved from the reaction mixture by filtration through a 45 μM membraneand the filtrate was concentrated. The residue was trituated with Et₂ O.The resulting white solid was collected and dried under vacuum to givethe title peptide of this example (51 mg, 53% yield, 92% pure asdetermined by HPLC).

EXAMPLE 6 Comparison of Acyclovir, the Peptide of Formula: Et₂CHNHCO--CH₂ CH[(S)-C(CH₃)₃ ]CO-Asp(pyrrolidino)-Asp(cyPn)-ΥMeLeu-OH, andthe Combination of the Two Agents in Inhibiting HSV-2 Replication inCell Culture

BHK-21/C13 cells (ATCC CCL 10) are incubated for two days in 150 cm²T-flasks (1.5×10⁶ cells/flask) with alpha-MEM medium (Gibco Canada Inc.,Burlington, Ontario, Canada) supplemented with 8% (v/v) fetal bovineserum (FBS, Gibco Canada Inc.). The cells are trypsinized and thentransferred to fresh media in a 24 well plate to give 2.5×10⁵ cells in750 μL of media per well. The cells are incubated at 37° C. for a periodof 6 hours to allow them to adhere to the plate. Thereafter, the cellsare washed once with 500 μL of alpha-MEM supplemented with 0.5% (v/v)FBS and then incubated with 750 μL of the same media (low serum) for 3days. After this period of serum starvation, the low serum medium isremoved and the cells are incubated in 500 μL of BBMT for 2 to 3 hours.[BBMT medium is described by P. Brazeau et al., Proc. Natl. Acad. Sci.USA, 79, 7909 (1982).] Thereafter, the cells are infected with HSV-2(multiplicity of infection=0.02 PFU/cell) in 100 μL of BBMT medium.(Note: The HSV-2 used was strain HG-52, see Y. Langelier and G. Buttin,J. Gen. Virol., 57, 21 (1981); the virus was stored at -80° C.)Following 1 hour of virus adsorption at 37° C., the media is removed andthe cells are washed with BBMT (3×250 μL). The cells in each well areincubated with or without (control) appropriate concentrations of thetest agent-dissolved in 200 μL of BBMT medium. After 29 hours ofincubation at 37° C., the infected cells are harvested by first freezingthe plate at -80° C., followed by thawing. The cells in each well arescraped off the surface of the well with the help of the melting icefragments. After complete thawing, the cell suspensions are collectedand each well is rinsed with 150 μL of BBMT medium. The viral sample(suspension plus washing) is sonicated gently for 4 minutes at 4° C.Cell debris are removed by centrifugation (1000 times gravity for 10minutes at 4° C.). The supernatant is collected and stored at -80° C.until determination of viral titer.

Viral titration was performed by a modification of the colorimetricassay method of M. Langlois et al., Journal of BiologicalStandardization, 14, 201 (1986).

More specifically, in a similar manner as described above, BHK-21/C13cells are trypsinized and transferred to fresh media in a 96 wellmicrotiter plate to give 20,000 cells in 100 μL of media per well. Thecells in the prepared plate are incubated at 37° C. for 2 hours. Duringthat time, the viral sample is thawed and sonicated gently for 15seconds, and log dilutions of the sample are prepared (1/5 sequential:50 μL of the sample plus 200 μL of BBMT medium, sequential dilutionsbeing done with a multichannel pipette.

On completion of the above 2 hour incubation of the BHK-21/C13 cells,the media is replaced with alpha-MEM medium supplemented with 3% (v/v)FBS. The cells are now ready to be infected with the various sampledilutions of virus. Aliquots (50 μL) of the various dilutions aretransferred into the appropriate wells of the plate. The resultinginfected cells are incubated for 2 days at 37° C. Then 50 μL of a 0.15%(v/v) solution of neutral red dye in Hank's Balanced Salt Solution (pH7.3, Gibco Canada Inc.) is added to each well. The prepared plate isincubated for 45 minutes at 37° C. Medium from each well is thenaspirated and the cells are washed once with 200 μL of Hank's BalancedSalt Solution. After the wash, the dye is released from the cells by theaddition of 100 μL of a 1:1 mixture of 0.1M Sorensen's citrate buffer(pH 4.2) and ethanol. [ Sorensen's citrate buffer is prepared asfollows: Firstly, a 0.1M disodium citrate solution is prepared bydissolving citric acid monohydrate (21 g) in 1N aqueous NaOH (200 mL)and adding sufficient filtered H₂ O to make 1 L. Secondly, the 0.1Mdisodium citrate solution (61.2 mL) is mixed with 0.1N aqueous HCl (38.8mL) and the pH of the resulting solution is adjusted to 4.2 ifnecessary.] The mixture in the wells is subjected to a gentle vortexaction to ensure proper mixing. The plate wells are scanned by aspectrophotometer plate reader at 540 mM to assess the number of viablecells. In this manner, the percentage of virus growth inhibition can bedetermined for the various concentrations of the test agent, and theconcentration of the test agent causing a 50% inhibition of virusreplication, i.e. the IC₅₀ can be calculated.

The following table is illustrative of the results obtained whenacyclovir and the title peptide of formula 1 were evaluated according tothe assay procedure of this example.

                  TABLE                                                           ______________________________________                                                       RANGE OF SAMPLE                                                               CONCENTRATIONS  IC.sub.50                                      COMPOUND       EVALUATED       (μM)                                        ______________________________________                                        acyclovir*      0.1 to 30 μM                                                                              4.0                                            peptide**        62.5 to 1000 μM                                                                          ˜1000                                    acyclovir +    0.005 to 30 μM                                                                             0.9                                            150 μM of peptide                                                          acyclovir +    0.005 to 30 μM                                                                             1.4                                            200 μM of peptide                                                          acyclovir +    0.005 to 30 μM                                                                             0.5                                            250 μM of peptide                                                          acyclovir +    0.005 to 30 μM                                                                             0.4                                            300 μM of peptide                                                          ______________________________________                                         *acyclovir was obtained from Bourroughs Wellcome Inc., Kirkland, Quebec,      Canada                                                                        **The title peptide of formula 1 of this example                         

The synergism of the combination of acyclovir and the peptide of formula1 can further be demonstrated by applying the isobole method to theabove results, see J. Suhnel, Antiviral Research, 13, 23 (1990) andreferences therein. The positive result obtained in the application ofthis method is illustrated graphically in the accompanying FIG. 1.

By following the procedure of this example, synergism can bedemonstrated also for other combinations of the nucleoside analogs andthe peptides of formula 1. Examples of other specific peptides offormula 1 for use according to the present invention are:

Et₂ CHNH-COCH₂ CH[(S)-C(CH₃)₃]CO-Asp(pyrrolidino)-Asp(cyPn)-{(S)-NHCH[CH₂ C(CH₃)₃ ]CH₂ OH}

Et₂ CHNH-COCH₂ CH[(S)-C(CH₃)₃ ]CO-Asp(pyrrolidino)-Asp(cyPn)-NHCH₂ CH₂C(CH₃)₃

Et₂ CHNH-COCH₂ CH[(S)-C(CH₃)₃ ]CO-Asp(pyrrolidino)-Asp(CyBu)-Leu-OH

Me₂ CHNH-COCH₂ CH[(S)-C(CH₃)₃ ]CO-Asp(NEt₂)-Asp-(diMe)-ΥMeLeu-OH

(Cyclohexyl)CH₂ NH-COCH₂ CH[(S)-CH(CH₃)₂]CO-Asp-(morpholino)-Asp(cyPn)-Cpg-OH

Me₂ CHCH₂ CH₂ NH-COCH₂ CH[(S)-Et]CO-Asp(piperidino)-Asp(cyBu)-Cha-OH.

The embodiments of this invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A pharmaceuticalcomposition for treating herpes infections in a mammal comprising apharmaceutically or veterinarily acceptable carrier, and the combinationof an antiherpes viral nucleoside analog, or a therapeuticallyacceptable salt thereof, and a ribonucleotide reductase inhibitingpeptide derivative of formula 1

    R.sup.1 NHC(O)CH.sub.2 CHR.sup.2 C(O)--NR.sup.3 --CH[CH.sub.2 C(O)--Y]C(O)--NH--CH[CR.sup.4 (R.sup.5)COOH]--C(O)--NH--CHR.sup.6 --Z

wherein R¹ is (1-10C) alkyl, (1-10C)alkyl monosubstituted with halo,hydroxy or lower alkoxy, lower cycloalkyl, (lower cycloalkyl)-(loweralkyl), phenyl(lower)alkyl or phenyl(lower)alkyl monosubstituted withhalo, hydroxy or lower alkoxy; R² is lower alkyl; R³ is hydrogen orlower alkyl; R⁴ is hydrogen or lower alkyl and R⁵ is lower alkyl, or R⁴and R⁵ together with the carbon atom to which they are attached form alower cycloalkyl; R⁶ is lower alkyl, lower cycloalkyl or (lowercycloalkyl)-(lower alkyl); Y is(a) NR⁷ R⁸ wherein R⁷ and R⁸ eachindependently is lower alkyl, or R⁷ and R⁸ together with the nitrogenatom to which they are attached form a pyrrolidino, piperidino,morpholino, thiomorpholino, piperazino or N⁴ -methylpiperazino; or (b)(1-7C)alkyl, lower cycloalkyl or (lower cycloalkyl)methyl; and Z ishydrogen, COOH or CH₂ OH;or a therapeutically acceptable salt thereof,wherein the antiherpes viral nucleoside analog and the peptide, are eachpresent in the composition in an amount effective to produce asynergistic effect in the mammal.
 2. A pharmaceutical composition ofclaim 1 wherein the peptide is a peptide of formula 1 wherein R¹ is(1-10C)alkyl, (1-10C)alkyl monosubstituted with halo, hydroxy or loweralkoxy, lower cycloalkyl or (lower cycloalkyl)methyl, R² is lower alkyl,R³ is hydrogen, R⁴ and R⁵ together with the hydrogen to which they areattached form a lower cycloalkyl, and R⁶, Y and Z are as defined inclaim 1; or a therapeutically acceptable salt thereof.
 3. Apharmaceutical composition of claim 2 wherein the peptide is a peptideof formula 1 wherein R¹ is 1-methylethyl, 1-methylpropyl, 1-ethylpropyl,1-methylbutyl, cyclopentyl or cyclohexyl, R² is methyl, ethyl, propyl,1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethylor 1-methylbutyl, R³, R⁴ and R⁵ are as defined in claim 2, R⁶ is1-methylethyl, 1,1-dimethylethyl, 1-methylpropyl, 2-methylpropyl,2,2-dimethylpropyl, cyclopentyl, cyclohexyl or cyclohexylmethyl, Y isNR⁷ R⁸ wherein R⁷ and R⁸ each independently is methyl, ethyl or propylor R⁷ and R⁸ together with the nitrogen atom to which they are attachedform a pyrrolidino, piperidino, morpholino or N⁴ -methylpiperazino, or Yis pentyl, hexyl, 4-methylpentyl, heptyl, cyclopentyl or cyclohexyl, andZ is as defined in claim 2; or a therapeutically acceptable saltthereof.
 4. A pharmaceutical composition of claim 3 wherein the peptideis a peptide of formula 1 wherein R¹ is 1-methylethyl or 1-ethylpropyl,R² is 1-methylethyl or 1,1-dimethylethyl, R³ is hydrogen, R⁴ and R⁵together with the carbon atom to which they are attached form acyclobutyl or cyclopentyl, R⁶ is 2,2-dimethylpropyl, Y isN,N-dimethylamino, N,N-diethylamino, pyrrolidino, morpholino or N⁴-methylpiperazino, hexyl, heptyl or cyclopentyl, and Z is as defined inclaim 3; or a therapeutically acceptable salt thereof.
 5. Apharmaceutical composition of claim 4 wherein the peptide is selectedfrom the group consisting of:Et₂ CHNH-COCH₂ CH[(S)-C(CH₃)₃]CO-Asp(pyrrolidino)-Asp(cyPn)-ΥMeLeu-OH Et₂ CHNH-COCH₂ CH[(S)-C(CH₃)₃]CO-Asp(pyrrolidino)-Asp(cyPn)-{(S)-NHCH[CH₂ C(CH₃)₃ ]CH₂ OH} and Et₂CHNH-COCH₂ CH[(S)-C(CH₃)₃ ]CO-Asp(pyrrolidino)-Asp(cyPn)-NHCH₂ CH₂C(CH₃)₃ ;or a therapeutically acceptable salt thereof.
 6. Apharmaceutical composition of claim 1 wherein the nucleoside analog is acompound of formula 2 ##STR2## wherein R⁹ is hydrogen, hydroxy or amino,or a therapeutically acceptable salt thereof.
 7. A pharmaceuticalcomposition of claim 1 wherein the antiherpes viral nucleoside analog isselected from the group of vidarabine, idoxuridine, trifluridine,ganciclovir, edoxudine, brovavir, fiacitabine, penciclovir, famciclovirand rociclovir.
 8. A pharmaceutical composition of claim 1 wherein theamount of the nucleoside analog, or a therapeutically acceptable saltthereof, is 0.01-1.0% by weight of the composition, and the amount ofthe peptide of formula 1, or a therapeutically acceptable salt thereof,is 0.5-20% by weight of the composition.
 9. A pharmaceutical compositionof claim 6 comprising 0.05-1.0% by weight of the compound of formula 2wherein R⁹ is hydroxy, and 1-10% by weight of the peptide of formula 1wherein R² is (S)-1,1-dimethylethyl, R⁴ and R⁵ together with the carbonatom to which they are attached form a cyclobutyl or cyclopentyl and R⁶is 2,2-dimethylpropyl.
 10. A cosmetic composition comprising anantiherpes viral amount of a combination of an antiherpes viralnucleoside analog of formula 2 ##STR3## in which R⁹ is hydrogen, hydroxyor amino, or a therapeutically acceptable salt thereof, and aribonucleotide reductase inhibiting peptide of formula 1

    R.sup.1 NHC(O)CH.sub.2 CHR.sup.2 C(O)--NR.sup.3 --CH[CH.sub.2 C(O)--Y]C(O)--NH--CH[CR.sup.4 (R.sup.5 COOH]--C(O)--NH--CHR.sup.6 --Z

wherein R¹ -R⁶, Y and Z are as defined in claim 1, or a therapeuticallyacceptable salt thereof, and a physiologically acceptable carrier,wherein the antiherpes viral nucleoside analog and the peptide, are eachpresent in the composition in an amount effective to produce asynergistic effect.
 11. A method of treating herpes viral infections ina mammal in need of such treatment, comprising administering thereto aneffective amount of a combination of an antiherpes viral nucleosideanalog, or a therapeutically acceptable salt thereof, and aribonucleotide reductase inhibiting peptide of formula 1

    R.sup.1 NHC(O)CH.sub.2 CHR.sup.2 C(O)--NR.sup.3 --CH[CH.sub.2 C(O)--Y]C(O)--NH--CH[CR.sup.4 (R.sup.5)COOH]--C(O)--NH--CHR.sup.6 --Z

wherein R¹ -R⁶, Y and Z are as defined in claim 1, or a therapeuticallyacceptable salt thereof, wherein the antiherpes viral nucleoside analogand the peptide, are each present in the combination in an amounteffective to produce a synergistic effect in the mammal.
 12. A method ofclaim 11 wherein the nucleoside analog and the peptide of formula 1 areadministered sequentially or simultaneously.
 13. A method of claim 11wherein the combination is administered topically.
 14. A method of claim11 wherein the antiviral nucleoside analog is selected from the group ofacyclovir, 6-deoxyacylovir,2,6-diamino-9-[(2-hydroxyethoxy)methyl]purine, vidarabine, idoxuridine,trifluridine, gangciclovir, edoxudine, brovavir, fiacitabine,penciclovir, famciclovir and rociclovir.
 15. A method of treating herpessimplex virus type 1 or type 2, infections in a mammal in need of suchtreatment, comprising administering thereto an effective amount of thepharmaceutical composition of claim 6 wherein the peptide of formula 1of the composition is selected from the group consisting of:Et₂CHNH-COCH₂ CH[(S)-C(CH₃)₃ ]CO-Asp(pyrrolidino)-Asp(cyPn)-ΥMeLeu-OH, Et₂DHNH-COCH₂ CH[(S)-C(CH₃)₃ ]-Asp(pyrrolidino)-Asp(cyPn)-{(S)-NHCH[CH₂C(CH₃ ]CH₂ OH}, and Et₂ CHNH-COCH₂ CH[(S)-C(CH₃)₃]CO-Asp(pyrrolidino)-Asp(cyPn)-NHCH₂ CH₂ C(CH₃)₃ ;or a therapeuticallyacceptable salt thereof.
 16. A pharmaceutical composition for treatingherpes infections in a mammal comprising a pharmaceutically orveterinarily acceptable carrier, and an effective amount of thecombination of an antiherpes vital nucleoside analog of the formula##STR4## or a therapeutically acceptable salt thereof, and aribonucleotide reductase inhibiting peptide of the formula

    Et.sub.2 CHNHCO--CH.sub.2 CH[(S)--C(CH.sub.3).sub.3 ]CO-Asp(pyrrolidino)-Asp(cyPn)-ΥMeLeu-OH

or a therapeutically acceptable salt thereof, wherein the antiherpesviral nucleoside analog and the peptide, are each present in thecomposition in an amount effective to produce a synergistic effect inthe mammal.